Centrifugal classifier for finely granulated solid substances in suspension



Apnl 22, 1958 c A. MAINO 2,831,575

CENTRIFUGAL CLASSIFIER FOR FINELY GRANULATED SOLID SUBSTANCES IN SUSPENSION Filed Dec. 2, 1955 CARLO ANTONIO MAINO INVENTOR.

I QQQ ATTORNEY United States Patent CENTRIFUGAL CLASSIFIER FOR FINELY GRANU- LATED SOLID SUBSTANCES IN SUSPENSION Carlo Antonio Maino, Cave del Predil, Italy, assignor to Raibl Societa Miniraria del Predil S. p. A., Cave (lei Predil, Udine, Italy, a corporation of Italy Application December 2, 1955, Serial No. 550,699

Claims priority, application Italy December 16, 1954 1 Claim. (Cl. 209-211) In many cases, in mechanical ore dressing there arises the need for a division as sharp as possible on a given size of a granulated solid substance, e. g. of a determined ore.

With conventional processes (grinding, fiotating) this size is in the order of the so-called very fines and the division of the granulated material into two fractions (one of size larger and the other of size smaller than a given size of granule) takes place with a very low classifying efliciency. The present invention affords a classifying machine which avails itself of a stronger held of settling force as due to centrifugation and acting upon a body of slurry inside the machine, kept in uniform agitation in such a way as to increase the efficiency of classification, making it sharper, keeping the potentialities of treatment high in respect of both time and space requirement.

The classifying machine embodying this invention includes a frustoconical drum rotatable about its horizontal axis and having solid walls provided with radial outlet apertures in the proximity of the base of smaller diameter and with the axial outlet holes provided in the base of larger diameter in the proximity of its periphery, the base of greater diameter being provided With an annular internal rim having an inner diameter smaller than that of a circle to which said axial outlet apertures are externally tangent, a hollow cylindrical body inside the drum and rotatable coaxially therewith, the walls of said body being provided with a plurality of through holes distributed uniformly and with a blade rigid therewith and wound helically there-around, and the border of which sweeps over the inner surface of the drum without touching it, and, further, a pipe for feeding the slurry being arranged coaxially with the drum to open freely into the aforesaid hollow cylindrical body. Said machine is diagrammatically represented in the accompanying drawing wherein:

Fig. 1 represents a longitudinal section and Fig. 2 represents a cross-section along the line AA of Fig. 1.

Referring to the drawing in detail, it will be seen that the classifying machine there illustrated includes a conical drum 4 with solid walls rotatable about its horizontal axis and provided with a plurality of radial apertures 6 in the proximity of the base of smaller diameter 11 and with a plurality of axial outlet apertures 7 distributed along a circle in the base wall 12 of large diameter. Rigid with the base wall 12 there is the internal annular rim 8 whose outer border is joined with the base wall 12 and whose inner border has a diameter smaller than that of the circle to which the apertures 2,831,575 assented Apr. 22, 1958 7 are externally tangent, in such a way that said rim covers completely the apertures 7 and operates as an overflow regularizing the outflow of the granulated fines.

Inside the drum 4 there rotates coaxially the hollow cylindrical body 2 into which there opens freely the pipe 1 for feeding the slurry wherein various granulated ore particles are suspended. Said cylindrical body 2 carries rigid with'its external wall a blade 3 helically wound around the body 2 and the edge of which sweeps over the internal surface of the wall of the drum 4 but without touching it, while a plurality of passage holes 9 provided in the wall of the cylindrical body 2 serve to fling the slurry like a spray into the interior of said drum 4.

Finally, it should be noted that the helical blade 3 is provided near its periphery, but spaced slightly therefrom so as to leave a solid outer strip, with a succession of slots 10 having the purpose of keeping the liquid in agitation continually.

The drum 4 receives movement from a belt 5 and pulley 5 and, moreover, it also transmits movement to the hollow body 2 through an epicyclic gear not shown in the drawings.

With that arrangement, the slurry fed continuously through the pipe 1 assumes the shape of a liquid annular cylinder inside the body 2 and through the holes 9 it is flung like a spray against the liquid body forming along the walls of the drum 4 and, while the helical blade continuously conveys the coarse portion settled on the wall of the drum towards the outlet apertures 6, the fine portion is expelled through the holes 7. The rim 8 which with the base wall 12 forms an annular chamber at Whose radial end there are provided the apertures 7, facilitates and regularizes the the flow of the fine portion and practically defines with its inner border the body of slurry contained in the drum, the inner cylindrical surface of which is=disposed radially outward with respect to the outlet apertures 6.

I claim:

A centrifugal machine for classifying finely granulated solid substances suspended in a slurry; said machine comprising a frusto-conical drum arranged with its axis extending horizontally and rotatable about said axis, said drum having base walls of relatively large and small diameters, respectively, at the opposite ends thereof, said drum having a circumferentially arranged series of radial outlet apertures therein adjacent said base wall of relatively small diameter and a circularly arranged series of axial outlet apertures in said base wall of relatively large diameter adjacent the outer periphery of the latter, an annular rim within said drum adjacent said base wall of relatively large diameter and extending radially inward beyond said axial outlet apertures of the latter, the inner diameter of said rim being greater than the inner diameter of said frusto-conical drum at the location of said circumferentially arranged series of radial outlet apertures, a hollow cylindrical body arranged coaxially within said drum and rotatable with respect to the latter, a helical blade on said body and dimensioned so that the outer edge of said blade is closely adjacent to the inner surface of the drum to sweep the latter in the direction toward said radial outlet apertures in response to relative rotation of said body and drum, a pipe extending axially into said body and opening freely within the latter for feeding a slurry containing relatively fine and relatively coarse particles of solid substances into said body, said hollow cylindrical body having a multitude of radially opening holes distributed uniformly therein between the turns of said helical blade for discharging slurry to be centrifuged into the interior of said drum, and said helical blade having a series of slots therein along the length of the blade, said slots being disposed adjacent to said outer edge of the blade and spaced a relatively small distance therefrom to leave a solid strip along said outer edge of the blade so that said solid strip of the blade can propel relatively coarse particles along the inner surface of the drum toward said radial outlet apertures, the slurry in the drum can References Cited in the file of this patent UNITED STATES PATENTS 2,054,058 Laughlin Sept. 8, 1936 2.46l,l29 Strezynski Feb. 8, 1949 2,703,676 Gooch Mar. 8, 1955 FOREIGN PATENTS 625,314 Great Britain June 24, 1949 

